Energetic electrons produced by shocks on the Sun

22 February 2019. Our Sun is an active star. Its activity manifests not only in the well-known 11-year Sun spot cycle but also in terms of short lived eruptions in its outer, hot atmosphere: the corona.

These events are known as flares and coronal mass ejections. The launch and expansion of ejected material can generate shock waves. On September 10th, 2017 the second largest flare of our present solar cycle occurred. It was accompanied by a very fast coronal mass ejection driving shock waves. This flare was well-observed with different space instruments and the ground based radio interferometer LOFAR.

Shocks driven by coronal mass ejections rapidly accelerate particles to high energies. The generation of such energetic electrons is of special interest in astrophysics, since they are responsible for the non-thermal radio and X-ray radiation in space. The relationship between coronal mass ejections, shocks and particle acceleration is a hot topic of present discussion. For the first time, the sites of electron acceleration were located at multiple places on the flanks of the expanding coronal mass ejection by means of LOFAR’s spatial and spectral capability.

LOFAR (LOw Frequency ARray) is a radio telescope network with a high spectral, spatial and temporal resolution. It presently consists of 24 core and 14 remote stations in the Netherlands and 13 international stations distributed in Europe with an extension of 1885 km from Ireland to Poland. The Leibniz Institute for Astrophysics Potsdam (AIP) participates with its own LOFAR station in Potsdam-Bornim and leads the key science project “Solar Physics and Space Weather with LOFAR”.